Tamperproof cylinder lock



Dec. 31, 1968 w. J. KERR 3,418,833

TAMPERPROOF CYLINDER LOCK Sheet of 2 Filed Aug. 15, 1966 WILLIAM J. KERR BY 5 A rry.

Dec. 31, 1968 w. J. KERR 3,418,333

TAMPERPROOF CYLINDER LOCK Filed Aug. 15. 1966 Sheet 2 of 2 INVENTOR WILLIAM J. KERR United States Patent 3,418,833 TAMPERPROOF CYLINDER LOCK William J. Kerr, Glenview, 11]., assignor to Chicago Lock Co., Chicago, IiL, a corporation of Illinois Filed Aug. 15, 1966, Ser. No. 572,555 4 Claims. (Cl. 70-421) ABSTRACT OF THE DISCLOSURE A tamperproof cylinder lock employing, in addition to the usual pin tumblers, a special radial tumbler which slides endwise in the lock plug near the mouth of the keyway and which interlocks with the lock cylinder to prevent turning of the plug within the cylinder during insertion of the key into the keyway. At such time as the key attains full projection into the keyway a socket in the key registers with the special tumbler and affords a clearance whereby such tumbler may move out of interlocking engagement with the cylinder to permit turning of the plug.

The improved tamperproof cylinder lock comprising the present invention is illustrated and described herein as assuming the form of an assembly comprising a sliding plate tumbler-type cylinder lock and a single-bitted key. The tamperproof features of the invention are, however, by suitable modification, if required, capable of being incorporated in other types of cylinder lock assemblies, regardless of whether they have single-bitted or doublebitted keys, or whether the tumblers are in the form of sliding plates, disks, or pins. Irrespective of the particular involved environment, the tamperproof features of the invention remain essentially or basically the same.

Contemplative pilferers of locks have long known that it is sometimes possible, often without much effort, to defeat or open a particular cylinder lock with an improper key by sliding the key bit back and forth in the keyway of the lock plug, while at the same time applying rotative torque or turning movement to the key. Although the particular key bit may not be designed to fit the particular lock under consideration so that when the key is fully introduced into the keyway, the tumbler splits (in the case of pin-type tumblers), or the tumbler ends (in the case of plate-type tumblers), do not clear the adjacent cylinder shoulders, at some intermediate point during the introduction or withdrawal of the key bit from the keyway, operative tumbler alignment may occur so that turning of the key and resultant turning of the plug are then possible. Small sliding plate tumbler-type cylinder locks, such, for example, as that which are used in connection with executive and secretary desks, file cabinets, and other items of office furniture, are particularly susceptible to this type of lock tampering and it is for this reason that such a lock has been selected for environmental purposes in disclosing the present invention.

According to the present invention, only a very slight modification of the cylinder and the plug assembly of a conventional sliding plate tumbler-type cylinder lock together with a similarly slight modification of the usual fiat key bit need be resorted to in order to obtain the tamperproof features of this invention. The plate-tumblers themselves, the associated springs, and the cylinder shoulders with which the tumblers cooperate remain unchanged, the modification consisting of the addition of a single auxiliary pin-type tumbler element which slides in a small radially extending bore in a portion of the plug body of the lock and the inner end of which cooperates with a socket in one side of the key bit. The other end of the auxiliary pin-type tumbler element cooperates with a notch which is formed or provided in the adjacent part of the "ice cylinder of the lock. The arrangement is such that when the key is fully inserted into the keyway in the lock plug, the auxiliary tumbler element enters the socket in the key bit and is withdrawn from the aforementioned notch in the cylinder to the end that the plug of the lock may be turned by the key. When the key is at any intermediate position within the keyway in the lock plug, the small auxiliary pin-type tumbler element does not seat in or enter the socket in the side of the key bit and is thus projected into the notch in the cylinder to the end that the plug may not be turned despite the fact that the usual plate tumblers may, by chance, be aligned so that otherwise they would permit turning of the plug by whatever key may be inserted in the keyway.

The provision of a tamper-proof cylinder lock of the character briefly outlined above and possessing the stated advantages and characteristics constitutes the principal object of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood.

In the accompanying two sheets of drawings forming a part of this specification, two illustrative embodiments of the invention are shown.

In these drawings:

FIG. 1 is an exploded perspective View of a cylinder lock assembly embodying the tamperproof features of one form or embodiment of the present invention;

FIG. 2 is a sectional view taken substantially centrally, longitudinally and vertically through the lock assembly of FIG. 1;

FIG. 3 is a side elevational view of the lock of FIG. 1 with a portion of the cylinder broken away and shown in section in order more clearly to reveal the nature of the invention;

FIG. 4 is a front end view or elevation of said lock;

FIG. 5 is a fragmentary sectional view of the lock of FIG. 1 showing the plug-releasing condition of the single auxiliary pin-type tumbler element when a proper key is fully inserted into the keyway in the cylinder of the lock;

FIG. 6 is a front elevational view of the structure that is shown in FIG. 5;

FIG. 7 is a fragmentary sectional view similar to FIG. 5 but illustrating the manner in which the single auxiliary pin-type tumbler element is forced or cammed inwardly v of the lock plug at the time torque is initially applied to the proper and fully inserted key of the lock;

FIG. 8 is a front elevational View of the structure that is shown or illustrated in FIG. 7;

FIG. 9 is a fragmentary view similar to FIGS. 5 and 7 but showing the lock in its unlocked condition with the pioper lock key in position in the keyway in the lock 1 a;

FIG. 10 is a front elevational view of the structure that is shown in FIG. 9;

FIG. 11 is a fragmentary view similar to FIGS. 5, 7 and 9 but illustrating the condition of the lock when an improper key is either fully or partially introduced into the keyway in the lock plug;

FIG. 12 is a front elevational view of the structure that is shown in FIG. 11;

FIG. 13 is a side elevational view of a proper key for the lock;

FIG. 14 is a longitudinal section of the key taken on the line 1414 of FIG. 13;

FIG. 15 is an enlarged side elevational view of the single auxiliary pin-type tumbler element which is employed in connection with, and constitutes the essential novel feature of the present invention;

FIG. 16 is an exploded fragmentary perspective view of the front portion of the lock cylinder that is associated with, and forms a part of, a modified form of the invention; and

FIG. 17 is a fragmentary, enlarged sectional view taken diametrically through the lock cylinder of FIG. 16 in the vicinity of a spring-biased pin tumbler element that is employed in connection with the modified form or embodiment of the invention.

Referring now to the drawings in detail and in particular to FIGS. 1 and 2, a cylinder lock of the sliding plate tumbler-type and embodying one form or embodiment of the present invention is designated in its entirety by the reference numeral 10. The special key for this lock is designated by the reference numeral 12 and is essentially a single-bitted key.

In many respects, the lock is conventional in that it includes a usual lock cylinder 14, a plug assembly 16, and a locking cam 18, these particular lock parts cooperating with one another in the usual manner so that only a brief description thereof to identify the constituent parts of the lock will be sufficient to constitute an environment for the tamperproof features of the present invention.

The lock cylinder 14 of the lock 10 is preferably in the form of a die casting and is provided on the front portion of the outer periphery with an external screw thread which is suitable for mounting the cylinder lock as a whole in a door or the like (not shown). The inner periphery or surface of the cylinder 14 is provided with the usual pair of longitudinally extending oppositely positioned ribs 19, the sides of which form shoulders which cooperate with the ends of the hereinafter referred to plate tumblers. The latter are carried by the plug assembly 16 in a manner well known in the art and will be only briefly described subsequently. An outwardly extending annular rim flange 20 is provided at the forward end of the cylinder 14 and this rim flange is provided in the front face thereof with an annular recess 21 which is defined by a circular bottom wall 21a and a cylindrical side wall 21b.

The plug assembly 16 includes a generally cylindrical plug body 22 having a longitudinal keyway 24 formed therein. Extending transversely across the central portion of the keyway is a longitudinal series of spaced apart plate tumblers 26. The latter are slidable in diametric fashion between the usual longitudinal series of spaced apart webs and are provided in their central portions with key-receiving slots 34. Such plate tumblers 26 have laterally extending shoulder-forming lugs 28 which are subjected to the biasing action of helical compression springs 30. The lug and spring arrangement is such that in the absence of the key 12 from the keyway 24, the upper ends of every other one of the plate tumblers 26 and the lower ends of the alternate plate tumblers project outwardly beyond the cylinder confines of the plug body 22. When the key 12, that is, the proper lock key, is fully projected into the keyway 24 as shown in FIG. 2, the contoured lower edge 32 of the bit or shank of the key cooperates with the lower edges of said key-receiving slots 34 in the plate tumblers to bring the upper and lower ends of all of the tumblers within the cylindrical confines of the plug body so that the plug assembly 16 may then be turned bodily as a unit under the influence of any manual torque or turning movement that is applied to the key 12. The forward end of the plug body 22 is formed with the usual radially extending rim flange 36 and it seats against the forward ends of the ribs 19 to limit the extent of rearward projection of the plug body into the cylinder 14. The rear end of the plug body 22 is formed with a square protuberance 38 which receives thereover a similarly squared hole 40 in one end of the locking cam 18. A screw 42 fixedly secures the cam in position on the plug body.

The arrangement of parts thus far described is purely conventional and no claim is made herein to any novelty in it, the novelty of the present invention residing rather in the nature of the hereinafter described and claimed tamperproof features which have been imparted to the otherwise conventional lock 10 and to the key 12 by means of which the lock may be operated between locked and unlocked or open positions.

As best shown in FIGS. 1, 3, 4, 5 and 6, the abovedescribed conventional sliding plate tumbler-type cylinder lock 10 is modified according to the present invention by the provision of a small diameter radial bore 50 in the extreme forward region of the plug body 22, this bore projecting completely through the wall of the plug body and being positioned at one side of, and at right angles to, the keyway 24. The inner end of the bore intersects and communicates with the interior of the keyway. The outer end of the bore 50 extends through the rim flange 36 on the front end of the plug body and since such rim flange nests within and substantially fills the recess 21 when the plug assembly 16 is in position within the cylinder 14, said outer end of the bore communicates with the recess while the inner end thereof communicates with the keyway 24 as previously pointed out.

Loosely and slidably disposed within the radial bore 50 is a single one-piece auxiliary pin-type tumbler element 52, the details of which are best illustrated in FIG. 15. This tumbler element 52 is generally of cylindrical design and has a reduced inner section 54 and a larger outer section 56. The reduced inner section 54 is formed with a frusto-conical distal end 58 and the larger outer section 56 is formed with a generally rounded distal end 60. The longitudinal extent, i.e., the length, of the tumbler element 52 is approximately equal to the radius of the plug body 22. Thus when there is no key in the keyway 24, the auxiliary pin-type tumbler 52 is capable of free floating movement in the bore 50 between the full line outer position of FIG. 3 and the broken line inner position of FIG. 4. In its inner position, the inner end of the auxiliary tumbler 52 serves to obstruct the entrance to the keyway.

The bore 50 is so disposed within the plug body 22 that when the lock is in its locked condition, the bore extends horizontally, and when the lock is in its unlocked condition, the bore extends vertically. In the locked condition of the lock, the outer end of the bore 50 registers with a notch 62 which is formed in the cylindrical side wall 21b of the recess 21, such surface being a part of the rim flange 20 at the front end of the cylinder 14. In the unlocked condition of the lock, the outer end of the bore 50 registers with a similar notch 64 which is formed in said cylindrical side wall of the recess 21 and is at an are or angle of from the notch 62, it being understood that the plug asembly 16 is capable of limited turning movement throughout an angle of 90 between its two extreme positions.

As shown in FIGS. 1, l3 and 14, the key 12 is generally of conventional design and embodies the usual key shank or bit 70, one side edge of which is grounded or otherwise shaped to form the aforementioned contoured edge 32. One side of the bit 70 of the key 12 is provided with the usual pair of longitudinally extending spaced apart milled grooves 72 for cooperation with the -usual inwardly extending projections (not shown) on the portion of the plug body 22 that defines one side of the keyway 24 as is customary with a conventional cylinder lock. The portion of the key shank that is between the grooves forms a longitudinally extending rib 75, the outer surface of which is flush or parallel with the bit side surface in which the grooves are formed. In the base or inner end of the rib 75 of the key bit 70 a socket 76 is formed, and this socket is designed to register with the frusto-conical distal end 58 of the reduced inner section 54 of the auxiliary tumbler element 52 when the key is fully inserted into the keyway 24. Shoulders 78 at the base of the key bit 70 limit the extent of projection of the key bit into the keyway and the socket 76 is positioned substantially in transverse alignment with these shoulders. The wall of the socket 76 is of conical configuration and the slant angle thereof is conformable to the slant angle of said frusto-conical distal end 58 of the reduced inner section 54 of the auxiliary pin-type tumbler element 52. The two notches 62 and 64 embody concave body surfaces which are semi-cylindrical in cross section but are of less than 180 extent in order that the rounded distal end 60 of the outer section 56 of the pin tumbler 52 is capable of being forced out of these notches by way of a camming action and under the influence of torque which is applied to the plug body 22 by the key 12 during the locking and unlocking operations of the lock. As shown in the drawings, the semi-cylindrical surfaces of the notches 62 and 64 are so arranged that the axes thereof are parallel to the axis of the cylinder 14, and the radius curvature of the outer end of the auxiliary tumbler element 52 is of less radius of curvature than the semi-cylindrical surfaces of the notches 62 and 64 in order to enhance the aforementioned camming action. Also as shown in the drawings, the front ends of the notches 62 and 64 extend through the front face of the rim flange 20 for keyway orienting purposes, said front face of the rim fiange being, in effect, the front end face of the cylinder 14.

The operation of the herein described cylinder lock is progressively illustrated in FIGS. 5 and 6, 7 and 8, 9 and 10, and 11 and 12 of the drawings. FIGS. 5 and 6 show the lock as it exists at the time the proper key 12 has been fully inserted into the keyway 24 and before any torque has been applied to the key for plug-turning purposes. It will be observed that the socket 76 in the inner end of the rib 75 of the key bit 70 is in radial alignment or registry with the auxiliary pin-type tumbler element 52 so that the latter has freedom of movement in a horizontal plane and within the bore 50. The tumbler element 52 is shown as having its rounded large outer end 60 seated within the notch 62. As soon as turning torque is applied to the key 12 tending to rotate the plug in a clockwise direction as viewed in FIG. 8 so as to commence unlocking operations, the rounded outer end 60 of the auxiliary pin tumbler 52 will make camming engagement with the semi-cylindrical surface of the notch 62 and the tumbler element 52 will be forced radially inwardly as illustrated in FIGS. 7 and 8 and until such time as the small frusto-conical inner end 58 of the tumbler element seats within the socket 76 in the key bit 70. At this time, the rounded outer end 60 of the auxiliary tumbler element 52 will clear the adjacent edge of the notch 62 and ride in the recess 21 under the continued application of torque to the key 12 and until the plug assembly 16 arrives at the position illustrated in FIGS. 9 and 10, this latter position representing the unlocked condition of the lock.

FIGS. 11 and 12 illustrate the manner in which the present lock defeats attempts to manipulate the lock, either by the use of an improper key or by sliding the proper key to an intermediate position within the keyway 24 where tumbler alignment will take place so that the plug assembly 16 may be turned within the cylinder. Since with an improper key not having a socket such as the socket 76 therein, no clearance space is aflorded for inward movement of the auxiliary tumbler element 52, the inner end of the tumbler will bear against the opposing side of the key bit 70 and the outer end of the tumbler will be disposed in the notch 62 (in the unlocked condition of the lock), or in the notch 64 (in the locked condition of the lock). Therefore, in the locked or unlocked condition of the lock, an improper key may not be used to rotate the plug assembly 16. Even with a key which is cut so as to have the plate tumbler-aligning contoured edge 32, unless the socket 76 is provided at the proper place on one side of the key bit, no lock operation is possible.

It is contemplated that tamperproof locks constructed according to the present invention will be used in group fashion throughout an entire business establishment, the only difference between the various keys being a difference in the contoured edges of the key bits. In such an instance, lock tampering with an unauthorized key having a socket such as the socket 76 therein is prevented. As soon as an operator, in attempting to defeat the lock by sliding the key axially in the keyway 24 while at the same time applying torque thereto, moves the key to a position where the socket 76 moves out of register with the auxiliary tumbler element 52, the condition set forth in connection with the illustration of FIGS. 11 and 12 will obtain and the auxiliary tumbler element 52 will be maintained with rounded outer end 60 seated in the notch 62 so that turning of the plug assembly 16 is prevented, despite the fact that occasionally a situation will arise where tumbler alignment takes place which, in the absence of the auxiliary tumbler element 52, would permit turning of the plug assembly.

Finally, the existence of the auxiliary tumbler element 52 very appreciably hinders attempts to defeat the lock by the use of various forms of lock-picking tools. With no key in the lock, the picking tool, when inserted into the keyway 24, maintains the tumbler element 52 in the position wherein it is shown in FIGS. 5 and 6, just as though a key bit were inserted in the lock. Thus, if the operator is successful in effecting tumbler alignment which otherwise would allow rotation of the plug assembly 16, he would have to withdraw the picking tool before the auxiliary tumbler element 52 could be coaxed from its nested position within the notch 62. As soon as the picking tool is withdrawn, the tumbler springs 30 will restore the plate tumblers 26 to a condition of misalignment, thus nullifying the effort of the operator to secure such alignment in the first place.

In the modified form of the invention which is shown in FIGS. 16 and 17, all of the elements of the lock assembly 10' remain substantially the same as the lock assembly 10 illustrated in FIGS. 1 to 15, inclusive, and as described herein with the sole exception that the auxiliary tumber element 52 which corresponds in structure and function to the auxiliary tumbler element 52 of the lock assembly 10 is biased radially outwardly to its outer position by means of a spiral compression spring 92'. The spring 92' bears at one end against an annular shoulder 93 which exists between the reduced section 54 and the larger section 96', and at its other end against a shoulder which is formed internally of the radial bore 50. Otherwise, the structure and the mode of operation of the lock assembly 10 is identical with the structure and operation of the lock assembly 10. In order to avoid needless repetition of description, corresponding parts as between the disclosure of FIGS. 1 to 15 and the disclosure of FIGS. 16 and 17 are designated with identical reference numerals, the prime sufiix being applied to such numerals in FIGS. 16 and 17.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. For example, where, in both of the herein illustrated and described embodiments of the invention, single auxiliary tumbler elements are employed, it is within the purview of the present invention to employ plural auxiliary tumbler elements all of which cooperate with respective sockets in the key bits in the manner heretofore described.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In combination, a tamperproof key-operated cylinder lock comprising a cylinder having formed in a front end face thereof an annular recess having a cylindrical side wall, a cylindrical plug rotatable within the cylinder between locked and unlocked positions and having formed therein a keyway, said plug being provided at its front end with an enlarged annular rim flange seated within and substantially filling said recess, a set of tumblers carried by said plug and individually shiftable endwise therein between cylinder-engaging and cylinder-releasing positions, spring means normally urging said tumblers to their cylinderengaging positions, said tumblers having portions thereof exposed in said keyway for cooperation with a key whereby upon projection of the key into the keyway to the fullest extent of which it is capable of being received the tumblers are moved to their cylinder-releasing positions, a key receivable in said keyway and provided with a contoured surface cooperating With said exposed portions of the tumblers, the forward region of said plug being formed with a radial bore which projects through said enlarged annular rim flange, said radial bore communicating at its inner end with said keyway, and communicating at its outer end with the cylindrical interface between the enlarged annular rim flange and the cylindrical wall of the internal annular recess, said cylindrical side wall of the recess being formed with a pair of circumferentially displaced internal notches, one notch registering with the radial bore in a locked position of the plug and the other notch registering with the radial bore in an unlocked position of the plug, an auxiliary one-piece tumbler-like element slidable in said radial bore between inner and outer positions when the bore is in register with either of said notches, said element when in an outer position having its outer portion disposed in either of said notches to lock the plug against rotation and having its inner portion withdrawn from the keyway, and when in its inner position having its inner portion projecting into the keyway and its outer portion withdrawn from either of said notches, said key being formed with a socket in a side portion thereof and in register with said bore when the key is fully inserted into the keyway, said socket affording a clearance region for movement of the element to its inner position, the portion of the key extending from said socket to the extreme distal end of the key being engageable with the inner end of said element and serving to prevent movement of the same to its inner portion, each notch being provided with a concave surface which makes camming engagement with the outer end of the auxiliary tumbler-like element to force the latter out of the notch and towards its inner position when turning torque is applied to the plug by the key.

2. The combination set forth in claim 1 and wherein the concave surface of each notch is of semi-cylindrical contour and is so arranged that the axis thereof is parallel to the axis of the cylinder, and the outer portion of the auxiliary tumbler-type element is rounded in order to enhance its camming cooperation with said concave surface of each notch.

3. The combination set forth in claim 2 and wherein the front end of the semi-cylindrical concave surface of each notch extends through the front end face of the cylinder.

4. The combination set forth in claim 2 and wherein the semi-cylindrical concave surface of each notch has a relatively large radius of curvature, and the rounded outer portion of the auxiliary tumbler-type element has a relatively small radius of curvature in order to enhance its camming cooperation with said concave surface of each notch.

References Cited UNITED STATES PATENTS 419,091 1/1890 Williams -421 X 758,024 4/ 1904 Taylor 70-421 1,835,725 12/1931 Thompson et al. 70-421 X 1,915,897 6/1933 Maxwell et al. 70421 X 2,145,085 1/1939 Heyer 70421 2,857,753 10/1958 Biro 70421 FOREIGN PATENTS 639,171 6/ 1950 Great Britain.

MARVIN A. CHAMPION, Primary Examiner. I

PERRY TEITELBAUMER, Assistant Examiner.

US. Cl. X.R. 70389, 406 

